Oil feed pump of chain saw

ABSTRACT

An oil feed pump of a chain saw is disposed in a chain saw crankcase. An adjustable pump cylinder is received in a crankcase cylindrical bore and has a pump plunger in said cylinder. A cam portion on the crankshaft reciprocates the pump plunger so that an oil passage which communicates with the cylinder bore delivers oil therein to be pumped to the point of use by the plunger.

United States Patent [191 Kobayashi et a1.

[ OIL FEED PUMP OF CHAIN SAW [75] Inventors: Torao Kobayashi, Tokyo; Hiromasa Miyata, Mitaka, both of Japan [73] Assignee: Kioritz Corporation, Tokyo, Japan [22] Filed: Oct. 17, 1972 211 App]. No.: 298,236

[52] U.S. Cl. 184/15 R, 184/27 R, 417/443 [51] Int. Cl. Fl6n 13/14 158] Field of Search 417/489, 443; 184/15 R, 184/15 A, 27 R [56] References Cited UNITED STATES PATENTS 3,530,957 9/1970 Shaw et al 184/15 R 2,768,587 10/1956 Corneil 417/443 3,288,072 11/1966 McKenzie 417/443 X [451 May 7,1974

3,448,829 6/1969 Rauh et a1 184/15 R 3,435,914 4/1969 Atsumi 184/27 R X 2,650,626 9/1953 Kiekhaefer 184/15 R X 1,990,408 2/1935 Kerst et a1 184/27' R X Primary ExaminerManue1 A. Antonakas Attorney, Agent, or FirmKarl W. Flocks 5 7] ABSTRACT An oil feed pump of a chain saw is disposed in a chain saw crankcase. An adjustable pump cylinder is received in a crankcase cylindrical bore and has a pump plunger in said cylinder. A cam portion on the crankshaft reciprocates the pump plunger so that an oil passage which communicates with the cylinder bore delivers oil therein to be pumped to the point of use by the plunger.

3 Claims, 3 Drawing Figures Pmmsnm H914 3.809.185 SHEET 1 OF 2 FIG. I

BACKGROUND OF THE INVENTION Conventional oil feed pumps of chain saws have generally been of the type which is provided as a plunger pump assembly to be fixedly mounted on the outer surface of a side wall of an engine crank case or at the other suitable location as by bolts and driven from an engine crank shaft through reduction gears, such as a worm and a worm gear.

In such type of oil feed pump, it has been generally impossible, after the oil discharge rate of the pump had once been set, to re-adjust said oil discharge rate by a simple manual operation, or it is required according to the prior art to provide a much complicated structure in order to re-adjust the oil discharge rate of the pump. Namely, for adjusting the oil discharge rate of the pump, it has been necessary to remove a cover of the crank case, etc. every time before a minute adjusting operation is performed.

Furthermore, an oil feed pump to be incorporated in a portable chain saw has been required to be as compact and simple as possible in construction and to be excellent in durability as well as in reliability, but the conventional oil feed pump has not necessarily been entirely satisfactory in respect of such requirements.

SUMMARY OF THE INVENTION It is, therefore, the object of the present invention to provide a novel oil feed pump for use in chain saws, which satisfies all of the requirements set forth above.

According to the invention, there is provided an oil feed pump of a chain saw, which comprises a cylindrical bore formed in the engine crank case of the chain saw extending at right angle to the crank shaft and being open in the outer surface of said crank case, a pump cylinder received in said cylindrical bore and having an adjusting knob fixed to one end projecting from the outer surface of the crank case, a pump plunger received in the axial bore of said pump cylinder and axially resiliently urged to a cam provided on said crank shaft by a spring means so as to make reciprocal motion directly following the rotation of said crank shaft, an oil passage open in the inner surface of said cylindrical bore and communicating with an oil tank formed in said crank case integrally therewith, an oil inlet port formed through the wall of said pump cylinder for communicating said oil passage with the axial bore of said pump cylinder, an oil outlet port tormed through the wall of said pump cylinder for discharging from the axial bore of said pump cylinder therethrough the oil trapped and compressed in said axial bore during the discharge stroke of said pump plunger, and thread engaging portions formed on the outer surface of said pump cylinder and the inner surface of said cylindrical bore for threadably engaging said pump cylinder with said cylindrical bore, said pump plunger reciprocating in the axial bore of said pump cylinder, whereby the oil is sucked into said axial bore from said oil inlet port and is discharged from said oil outlet port, and said knob being manually rotated to adjust the position of said pump cylinder and hence the position of said oil inlet port while the stroke position of said pump plunger being maintained unchanged at all times, whereby the oil discharge rate is adjusted.

The oil feed pump of the invention constructed as described above, therefore, has the following advantages:

i. The oil discharge rate can be adjusted by a very simple operation by rotating manually the knob protruding from the outer surface of the crank case and thereby minutely adjusting the position of the oil inlet port of the pump cylinder relative to the pump plunger.

ii. The oil feed pump of the invention can be designed in a very compact form as it is completely accommodated within the crank case of the engine.

iii. The oil feed pump of the invention does not call for transmission means and is inexpensive as it is a plunger type pump of the simplest construction and the reciprocal motion of the pump plunger is effected directly by the cam provided on the crank shaft.

iv. The oil feed pump of the invention is highly durable and reliable in operation and readily to be put under the work of inspection and maintainance thereof, as its construction is simple and involves a minimum number of sliding portions.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional view of the oil feed pump of a chain saw, according to the present invention;

FIG. 2 is a sectional view of the essential portion of the oil feed pump, illustrating the relationship between the position of the oil inlet port of 'the pump cylinder of the pump and the stroke of the pump plunger; and

FIG. 3 is a diagram illustrating the oil discharge rate characteristic of the oil feed pump of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 is a sectional view provided to show the construction of the oil feed pump of the invention which is incorporated in an engine of a chain saw. In FIG. 1, reference numeral 10 designates a crank case of the engine, 12 a crank shaft rotatably supported in said crank case, and 14 a conventional centrifugal clutch mounted on that portion of the crank shaft which is projecting outwardly from said crank case. A sprocket 16 is fixed to the driven member (outer drum) of the centrifugal clutch. As is well known, this sprocket 16 is rotated from the crank shaft through the centrifugal clutch when the rotating speed of said crank shaft increases beyond a predetermined value, thereby to drive a saw chain engaged therearound.

Now, the construction of the oil feed pump of the invention will be described.

A cylindrical bore 20 is formed at a suitable location (preferably at a portion adjacent the centrifugal clutch) at right angles to the crank shaft 12. An oil passage 22 is opened in the cylindrical bore 20 intermediate the axial length of said cylindrical bore. This oil passage 22 is in communication through an oil conduit 24 with an oil tank 26 formed integrally with the crank case.

A pump cylinder 30 is disposed in the cylindrical bore 20 in sealing engagement therewith. The pump cylinder 30 is formed at the upper portion with external threads 32 which are in engagement with internal threads formed at the upper portion of the cylindrical bore 20. Further, the pump cylinder 30 is provided with an adjusting knob 34 which is fixed to the upper end of said pump cylinder projecting outwardly from the outer surface of the crank case. Thus, it will be understood that, by rotating the knob 34 manually, the axial position of the pump cylinder 30 can be finely adjusted.

Reference numeral 36 designates an elastic spring seat interposed between the knob 34 and the crank case, by which the pump cylinder is retained immovably in its adjusted position. An oil inlet port 38 is formed through the wall of the pump cylinder 30 in communication with the axial bore of said pump cylinder, at a location substantially opposite to the opening of the oil passage 22. Further, a recess 38 is formed in the outer surface of the pump cylinder 30 in communication with the oil inlet port 38. This recess 38' has a size large enough to secure the communication between the oil inlet port 38 and the oil passage 22 over the entire range of axial movement of said pump cylinder for positional adjustment. A ball 40 serving as a check valve is disposed in the axial bore of the pump cylinder 30 above the oil inlet port 38. This ball 40 is urged downwardly under a predetermined biasing force by a spring 42 and a closure member 44 disposed in the upper portion of the axial bore of the pump cylinder 30. Therefore, it will be understood that oil is allowed to flow upwardly through the check valve only when a pump plunger 50, slidably received in the lower portion of the axial bore of the pump cylinder 30, is in its upward or discharge stroke. The oil having flowed upwardly through the ball 40 is discharged from the pump cylinder 30 through an oil outlet port 46 formed through the wall of said pump cylinder and led to places desired to be lubricated through suitable oil conduits. At the outer peripheral of said pump cylinder there is formed an annular recess which serves to positively keep the oil flow communication between said outlet port 46 and said oil conduit regardless to the readjustment of said pump by screwing into or out said pump cylinder.

As stated, the pump plunger 50 is slidably received in the axial bore of the pump cylinder 30. The upper end of the pump plunger 50 is located at the position of the oil inlet port 38 and the lower end thereofis resting on a cam 52 provided on the crank shaft 12. Between the lower end of the pump cylinder 30 and a large diameter portion formed at the lower end of the pump plunger 50 is interposed a compression spring 54 to urge the lower end face of said pump plunger against the cam surface of the cam 52 with a suitable pressure and thereby to ensure positive movement of said pump plunger by said cam. In this way, said pump cylinder 30 and said pump plunger 50 are independently constructed with respect to each other so that the adjustment of the oil pump may be effected only by manually changing the position of said pump cylinder, while the stroke position of said pump plunger being maintained unchanged at all times.

In FIG. 1, there is disclosed a type of cam as formed integrally in the crank shaft 12, and in this embodiment reciprocal movement of the pump planger 50 may be effected whenever the crank shaft rotates, namely, whenever the engine is in operation. In place of such type of cam, another type of cam that is fixedly connected to the output side of a centrifugal clutch 14 may be used so that said pump plunger is reciprocated only when the rotational speed of said crank shaft exceeds a predetermined value. When the rotational speed of the crank shaft is less than the predetermined value, the centrifugal clutch 14 is released, this resulting in said cam being ceased and thus said pump plunger also being ceased.

The oil outlet port 46 is communicated through oil passages formed in the crank case with the surface of a saw bar and other places of the chain saw desired to be lubricated.

O-rings are fitted around the outer peripheral surface of the pump cylinder below the oil inlet port, between said oil inlet port and the oil outlet port and at a suit able location above said oil outlet port to ensure sealing between the pump cylinder 30 and the cylindrical bore 20 to prevent leakage of oil.

The oil feed pump of the invention constructed as described above operates in the following manner:

Namely, when the engine is set in motion and the crank shaft is rotated, the pump plunger 50 is caused to make a reciprocal movement by the cam 52 provided on said crank shaft. The total stroke of this reciprocal movement is about 1.5 mm. The reciprocal movement of the pump plunger consists of a suction stroke in which the plunger opens the oil inlet port and an upward or discharge stroke in which said plunger closes said oil inlet port, as shown in FIG. 2, whereby suction and discharge of oil, i.e. a pumping operation, is performed.

The discharge characteristic of the pump of this invention is illustrated in FIG. 3 and it will be seen from FIG. 3 that, since the total stroke of the plunger is constant and about 1.5 mm. an increase of the discharge stroke results in a decrease of the suction stroke and, conversely, an increase of the suction stroke results in a decrease of the discharge stroke. Therefore, it will be understood that the discharge of the pump is almost maximum when the position of the pump cylinder relative to the pump plunger has been adjusted by rotating the adjusting knob such that the quantity of oil sucked in the suction stroke may be substantially equal to the quantity of oil discharged in the discharge stroke.

In a position of the pump cylinder deviating from the aforesaid position in which the quantities of oil sucked and discharged are substantially equal, the actual discharge of the pump is determined by the smaller one of the quantity of oil sucked in the suction stroke and the quantity of oil discharged in the discharge stroke subsequent to closure of the oil inlet port. For instance, even with the pump cylinder being in a lower position to achieve a theoretical discharge rate of 20 cc/min, the actual discharge rate will be 10 cc/min if the effective suction rate is 10 cc/min and, conversely, even with the pump cylinder being in a position to achieve a theoretical suction rate of 20 cc/min, the actual discharge rate can also be limited to 10 cc/min if the effective discharge rate is only 10 cc/min.

Shifting the pump cylinder position upwardly by rotating the adjusting knob will result in an increase of the suction stroke, whereas shifting of the same downwardly will result in an increase of the discharge stroke. However, when the pump cylinder is in the position to achieve the maximum discharge rate, i.e. in the position in which the quantity of oil sucked in the suction stroke and the quantity of oil discharged in the discharge stroke are substantially equal, rotation of the adjusting knob in either direction will result in an decrease of the oil discharge rate. In practice, the position of the pump cylinder to achieve the maximum discharge rate is determined by the fine adjustment of the cylinder position while observing the quantity of oil actually being discharged. Namely, the pump cylinder can be set in the maximum discharge rate position with sufficient accuracy, only by the observation of the actual flow rate and dropping state of the oil.

We claim:

1. An oil feed pump of a chain saw, comprising a cylindrical bore formed at a portion of the crank case extending at right angles to a crank shaft rotatably supported in said crank case and being open in the outer surface of said crank case, and a pump cylinder received in said cylindrical bore and having an adjusting knob at its end projecting from the outer surface of said crank case, said pump cylinder being threadably engaged in said cylindrical bore with external threads formed on the outer surface thereof in engagement with internal threads formed on the inner surface of said cylindrical bore so that its axial position may be finely adjustable in said cylindrical bore, and further comprising a pump plunger axially reciprocally received in the axial bore of said pump cylinder and independently constructed with respect to said pump cylinder, said pump plunger being urged at all times to a cam formed on said crank shaft so as to constantly maintain the stroke position of said pump plunger, an oil passage open in the inner surface of said cylindrical bore and communicating with an oil tank, an oil inlet port formed through the wall thereof for communicating said oil passage with the axial bore thereof, check valve means disposed in the axial bore thereof and adapted to permit passage of oil only in an oil discharging direction incident to the reciprocal movement of said pump plunger, and an oil outlet port formed through the wall thereof for discharging the oil having passed through said check valve means, whereby the oil is discharged by the pump plunger reciprocating in a constant stroke determined by the rotation of said cam on said crank shaft and the amount of oil being discharged can be varied by the relative position of said oil inlet port to said pump plunger, said relative position being changed by adjusting the position of said pump cylinder, independently from the position of said pump plunger.

2. An oil pump of a chain saw as defined in claim 1, in which the reciprocating movement of said pump plunger is effected by means of said cam, said cam being integrally formed on said crank shaft so that said oil pump may be operative whenever said crank shaft is rotated.

3. An oil pump of a chain saw as defined in claim 1 wherein said pump cylinder is formed with a recess in its outer surface, said recess being in communication with both said oil inlet port and said oil passage over a predetermined range of axial movement of said pump cylinder whereby continuity of operation is ensured when position adjustment of said pump cylinder is desired to vary the flow rate therethrough. 

1. An oil feed pump of a chain saw, comprising a cylindrical bore formed at a portion of the crank case extending at right angles to a crank shaft rotatably supported in said crank case and being open in the outer surface of said crank case, and a pump cylinder received in said cylindrical bore and having an adjusting knob at its end projecting from the outer surface of said crank case, said pump cylinder being threadably engaged in said cylindrical bore with external threads formed on the outer surface thereof in engagement with internal threads formed on the inner surface of said cylindrical bore so that its axial position may be finely adjustable in said cylindrical bore, and further comprising a pump plunger axially reciprocally received in the axial bore of said pump cylinder and independently constructed with respect to said pump cylinder, said pump plunger being urged at all times to a cam formed on said crank shaft so as to constantly maintain the stroke position of said pump plunger, an oil passage open in the inner surface of said cylindrical bore and communicating with an oil tank, an oil inlet port formed through the wall thereof for communicating said oil passage with the axial bore thereof, chEck valve means disposed in the axial bore thereof and adapted to permit passage of oil only in an oil discharging direction incident to the reciprocal movement of said pump plunger, and an oil outlet port formed through the wall thereof for discharging the oil having passed through said check valve means, whereby the oil is discharged by the pump plunger reciprocating in a constant stroke determined by the rotation of said cam on said crank shaft and the amount of oil being discharged can be varied by the relative position of said oil inlet port to said pump plunger, said relative position being changed by adjusting the position of said pump cylinder, independently from the position of said pump plunger.
 2. An oil pump of a chain saw as defined in claim 1, in which the reciprocating movement of said pump plunger is effected by means of said cam, said cam being integrally formed on said crank shaft so that said oil pump may be operative whenever said crank shaft is rotated.
 3. An oil pump of a chain saw as defined in claim 1 wherein said pump cylinder is formed with a recess in its outer surface, said recess being in communication with both said oil inlet port and said oil passage over a predetermined range of axial movement of said pump cylinder whereby continuity of operation is ensured when position adjustment of said pump cylinder is desired to vary the flow rate therethrough. 